Verilink AS2000: The Basics (880-502981-001) Product Manual - Manual (Page 159)

Acronyms and Definitions
Verilink Access System 2000: Basics Glossary-39
PROM Programmable Read-Only Memory.
protocol The set of rules governing the
format, timing, sequencing, and
error control of exchanged
messages over a network or
between devices. Needed for data
transfer and communication
between two directly connected
organized units.
PSES P-bit Severely Errored Seconds. A
second during which a DS3 circuit
experiences 44 or more PCVs OR
one or more Out of Frame defects
OR a detected incoming AIS. The
PSES count does not increase when
UASs are counted.
public switched telephone network
(PSTN)
The public network operated by
carriers who provide leased lines
and packet-switched circuits so
users can connect customer site
equipment for data
communications. Sometimes
referred to as a private network.
PVC See Permanent Virtual Circuit
(PVC) .
PWR 2940 A power supply for use with a
Dual-line Shelf (DLS). See
universal power supply (PWR
2940) .